A wide variety of communications services are available to a user of a modem public switched telephone network (PSTN). Such services include voice mail systems, interactive voice response (IVR) systems, and personal identification number communication systems. Each of those services operates by supplying audio information, such as instructions or messages, to the user via a conventional wireline or wireless telephone. In response to the audio information, the user generally can select a desired service or a source of information by pressing one or more predetermined buttons on the dial pad of the telephone.
For example, IVR systems are used to implement services that supply audio information to users via the PSTN. In general, a user dials a telephone number associated with a selected IVR information service to listen to audio information directed to a subject of interest to the user. The IVR information service responds to the call by offering a voice menu of information selections. The user selects the desired information item by pressing one or more predetermined buttons on the telephone dial pad. However, IVR information services often lead users through a daunting number of instructions and dial pad presses before the caller receives the desired audio information. When listening to an extended set of instructions, a caller is often faced with writing notes to memorialize the instruction set prior to responding to the instructions to obtain the desired information. Accordingly, IVR information services can be difficult for a caller to effectively use because the caller typically must remember and correctly respond to a set of instructions prior to hearing the desired information.
In recognition of this disadvantage of present audio-based communications services, the telecommunications industry has developed a system that supplements the audio information supplied from voice-based communications services by transmitting data over the telephone line for presentation by a visual display located on a specially adapted telephone. The system is implemented by using an analog telephone line instead of an ISDN telephone line because an ISDN telephone line is at present less cost-effective than an analog line. By supplying both audio and visual information over the analog telephone line, the system provides added value to communication services offered via the PSTN, promotes increased telephone usage, and defines a transition path for the eventual use of ISDN technology for such data display applications.
A prior art system transmits data to an ADSI-compatible telephone using a bi-directional communications protocol based upon dual tone multiple frequency (DTMF) and BELL 202 modem signaling. A call placed to a preselected telephone number associated with a service is routed through the end office to a service switching point, specifically a Northern Telecom Model DMS-100. In response to the call, the service switching point transmits data and instructions to the ADSI-compatible telephone. The data generally includes textual information associated with the selected service and softkey labels corresponding to softkeys on the ADSI-compatible telephone, and instructions for the ADSI-compatible telephone. An initial instruction is transmitted as a DTMF signal and textual information, softkey labels, and subsequent instructions are transmitted as BELL 202-compatible modem signals. When the user presses a softkey, the ADSI-compatible telephone initiates a resident action or transmits a DTMF signal assigned to the softkey and the system responds by updating the data presented by the display of the ADSI-compatible telephone. This information update is completed by downloading responsive textual information and softkey labels to the ADSI-compatible telephone. The service is terminated when the user returns the telephone handset to an on-hook position.
A critical limitation of the prior art system is that the implementation for the ADSI communications service is constrained by the capabilities of the equipment installed for a typical telephone network including the end office and the service switching point. This equipment is generally designed for general purpose telephone-related applications and often does not facilitate the rapid and efficient implementation of a specific ADSI service by a service provider.
Accordingly, there is a need for a system that is capable of supplying data for visual display by an ADSI-compatible telephone and can be quickly installed by a service provider within the framework of an existing public switched telephone network. In particular, there is a need for an ADSI system that is implemented by connecting a service circuit node, which is programmable by the service provider for a specific ADSI service, to an existing service switching point. The present invention uses a service circuit node and an adjunct processor having BELL 202 modem and DTMF signaling functions to implement a communications service for displaying textual information via the PSTN.